Data is stored on magnetic media by writing on the magnetic media using a write head. Magnetic media can be formed in any number of ways, such as tape, stripe, floppy diskette, and hard disk. Writing involves storing a data bit by utilizing magnetic flux to set the magnetic moment of a particular area on the magnetic media. The state of the magnetic moment or bit transition is later read, using a read head, to retrieve the stored information.
An important goal of the magnetic storage industry is to improve data density. Data density is determined by the amount of data stored on an area of magnetic media and depends on how much area must be allocated to each bit. Both track density, a measure of how closely the tracks are spaced, and linear density, a measure of how closely the bits are spaced along the track, determine the overall data density.
To improve data density, reduced size write head structures and high coercivity media are used. A typical write head such as disclosed in U.S. Pat. No. 5,452,164, by Cole et al., entitled THIN FILM MAGNETIC WRITE HEAD, issued Sept. 19, 1995, herein incorporated by reference in its entirety, employs pedestal poles tips to improve track density. Furthermore, to improve linear density, bits are spaced closer together. Higher linear density, though, necessitates higher data rates. Thus, the rate that data is stored to the media also is an important measure of the operational performance of the write head.
The data rate is determined by the characteristics of the materials and the structure of the write head. In some stitched pole writers, the pole tips are made of FeNi with 35%-55% Fe so that the pedestal pole tips can supply the increased flux necessary to set bits on the high coercivity media.
Using FeNi with 35%-55% Fe, however, has been observed by the present inventors to cause stripe domains 10 and 20 to form in the pedestal pole tips as illustrated in FIG. 1. FIG. 1 is a view from the air bearing surface showing longitudinal stripe domains 10 and 20, which form in an FeNi upper pedestal pole tip P2T having 45% Fe, during operation. The stripe domains 10 and 20 represent magnetic moments facing in and out of the page, respectively, as detected by a magnetic force microscope. By comparison, the lower pedestal pole tip P1T, formed of permalloy, shows magnetization domain states in the plane of the paper. These longitudinal stripe domain patterns largely degrade write head efficiency and cause a degradation of the Non Linear Transition Shift or NLTS, a key write performance parameter, at higher linear density.
What is needed is a writer with improved performance at high data density and high data rate.
A preferred embodiment of the present invention provides a thin film write head having upper and lower pole structures each having pedestal pole tips formed with CoNiFe. In a preferred embodiment, the pedestal pole tip of the upper pole structure and the pedestal pole tip of the lower pole structure comprises from about 60% to about 70% Co and from about 10% to about 15% Ni. High Bsat CoNiFe provides high flux across the write gap necessary for writing to high coercivity media, thus allowing for high data density. In addition, it provides low magnetostriction to inhibit stripe domains and xe2x80x9cpopcorn noisexe2x80x9d.
The upper pole structure of the preferred embodiment of the present invention has a laminated yoke portion having upper and lower layers. The lower layer is stitched to the pedestal pole tip of the upper pole structure and comprises FeXN, where X is selected from the group consisting of Rh, Ta, Hf, Al, Zr, Ti, Ru, Si, Cr, V, Si, Sr, Nb, Mo, Ru, and Pd. FeXN has a faster rise time and a better damping constant. As such, FeXN may provide a shorter exchange rate or magnetization rotation time, which allows for higher data rates.
The upper layer comprises NiFe preferably having from about 15% to about 55% of Fe. With the preferred embodiments and methods, the lower layer of the yoke is defined by etching FeXN material using the upper layer as a hard mask. The upper pole structure and method of the present invention allows for improved geometries and process control.
In a preferred method and embodiment, the top surfaces of the conductor coil and the upper pedestal pole tip are planarized and an inorganic capping layer formed over the planar surface. The inorganic capping layer may be used to insulate the conductor coil from the yoke and to provide a low apex angle to form the yoke over.